Advanced search operators (proximity, INTERSECTS, ANDEQUALS) will use the old search engine.

Due to the way Chinese and Korean are indexed, the new search engine will not be used for CJK searches.

The new search engine will automatically fall back to the existing search engine if it can't support the current query or search type. Thus, no search functionality is removed by enabling the new search engine.

It's not always easy to tell whether the new search engine or the old one was used for a particular search.

Some Guide sections (that use simple searches as described above) will benefit from the new search engine if it's enabled.

The new search engine requires a 64-bit operating system (32-bit Windows users are not supported).

Known Issues

Cited By may show "-1 results" when "Sort results by search rank" is enabled in the Cited By panel menu.

A quick test of this suggests that for simple searches, the reported performance is significantly quicker. As a minimum it's about three times quicker than the old search. For searches with millions of results, it might be 30 times quicker.

I notice small discrepancies in a "By Resource" count (158,789 results vs. 158,613 results in one test, 2,061,881 vs 2,061,665 in another, 12,903,925 vs 12,893,978 in a third).

I find it odd that we can't get counts with a Ranked new search. You can run the "Ranked" and the "By Resource" search quicker than the old "Ranked Search" on its own. When necessary, why not run a background "By Resource" search to get the counts?

When running searches with relatively few results (thousands, not millions) "Your books" can be slower under the new search engine (about half the speed of before).

I notice small discrepancies in a "By Resource" count (158,789 results vs. 158,613 results in one test, 2,061,881 vs 2,061,665 in another, 12,903,925 vs 12,893,978 in a third).

The new search engine will count multiple occurrences within one footnote as a single "hit", whereas the old search engine would count them multiple times. This should have been in the release notes; I'll update them.

(If you notice hit count discrepancies when searching just surface text, that could be a problem.)

Can you, in a nutshell, explain what the new search engine will do as compared to the current one? Are we to expect (when it is fully developed and implemented) only search speed improvements or are there also other performance enhancements (e.g., a better ranking algorithm) or added/different functionalities?

Ranked search is much more improved than "By Resource". Also, the more results, the greater the difference. A ranked search for "the" in my library gives 2.23s compared to 60.68s (x27). For "By Resource", it's 19.07 vs 82.48 (x4).

Can you, in a nutshell, explain what the new search engine will do as compared to the current one? Are we to expect (when it is fully developed and implemented) only search speed improvements or are there also other performance enhancements (e.g., a better ranking algorithm) or added/different functionalities?

You can expect speed improvements for now. We'll announce other changes when they become available.